we've eaten there twice, the first time as a party of two...we were seated in the backseat of a two-seater car. The young couple in front smiled when our waitress referred to us as parental-type hitchhikers, so no hanky-panky in the front seat (they were actually newlyweds on honeymoon, too.) That was it for total interaction between front & back seat. The screen is high enough, everyone in the car can see well.
The second time we ate there, we were a party of 4 and were again sat in a 2-seater car so it was just the 4 of us. But even then, my son & his wife were in the front seat and it really is not conducive to conversation between front & back...because of the stationary table & bench seat construction, it's not really comfortable for the people in the front seats to turn around and chat with the people behind....and the noise level of the movie clips is pretty loud so it was difficult to hear the people behind you.
My general impression is that about 1/2 the cars in Sci-Fi have 2 seats, about 1/2 have 3 seats. There are also a few that are basically set up as regular tables with chairs (they just have a car-front and back on the ends of the table. ) Those are mostly for parties of 6 or families with toddlers/babies needing high chairs.